Sound insulation performance of cube-shaped enclosure

The subject of the research described in the article are the sound insulating properties of a cube-shaped enclosures, the walls of which are made of plates of homogeneous materials and two-layer baffles. As an enclosure for an omnidirectional sound source imitating a noisy machine or device, a prototype test stand for testing the acoustic properties of materials and enclosures was used. The three tested variants were enclosures with walls made of plastic plates, such as polyethylene, solid polycarbonate, and plates in the form of rigid polyethylene foam. The fourth variant was an enclosure with walls made of sandwich baffles in the form of a steel plate with a rubber layer glued on. Calculations of the effectiveness of the enclosure were carried out using the previously developed theoretical calculation model for insertion loss (IL). The obtained results were related to the IL obtained in the course of experimental tests. The research showed slight discrepancies between the calculations and the measurement results for almost all tested materials in the entire frequency range (100-5000 Hz), with the exception of rigid polyethylene foam, for which the discrepancies were relatively the largest in the lower frequency range, i.e. below 400 Hz. Research has shown that the best sound insulation performance was achieved for an enclosure with two-layer walls.